It has heretofore been proposed to provide covers of small receptacles which spring open when a latch is released as in U.S. Pat. No. 490,433 to Goertz of Jan. 24, 1893 wherein a coil spring around the hinge throws the cover of a bag open when a spring catch is released. Distorting the metal of a bag cover is disclosed in U.S. Pat. No. 1,505,393 to Kasdan of Aug. 19, 1924 for springing the cover open when a latch is released while the cover is urged to closed position by a coil spring hinge in U.S. Pat. No. 1,473,972 to Prahar of Nov. 13, 1923.
The coil spring hinges of the relatively small receptacles and covers of the above mentioned patents, and larger size coil spring hinges of various types commercially available have not been found suitable for spring opening the lid of attache cases, cassette cases and luggage because the spring becomes so large as to be awkward in appearance and to make the hinge portion unduly prominent and visible.